Various different arrangements of springs, padding and energy absorbing devices have been utilized in an attempt to decrease the recoil energy felt from the impact of the butt end of a firearm stock on the shoulder of a shooter.
Although not related to recoil apparatus for shoulder fired guns, the most relevant prior art is that found in the U.S. Pat. No. to Balleisen, et al., U.S. Pat. No. 2,701,963. An experimental machine gun mount is disclosed in which the vibration frequency and amplitude can be varied to obtain the highest rate of fire from the gun. Part of the mounting apparatus includes a plurality of calibrated Belleville springs stacked on a pair of parallel rods. By variously arranging the springs in series, parallel or parallel-series, more or less resistance may be provided to oppose recoil of the gun and various conditions due to the gun fire may be determined by the number and arrangement of the springs employed. While this patent discloses the use of Belleville springs to absorb the energy of a firing gun, it does not teach or suggest the advantages and construction related to using the springs inside the stock of a shoulder fired rifle, nor the other necessary mechanical elements which are necessary to absorb the energy of a shoulder firearm and, at the same time, provide for stock length adjustment, as in the present invention.
In U.S. Pat. No. 4,164,825, Hutchison discloses a recoil reducing device comprising a piston suspended in a closed chamber filled with a viscous liquid. The piston includes outwardly or radially extending means which resist rapid movement of the piston in the liquid, thereby achieving some reduction in gun recoil speed which has a damping effect for recoil reduction. The structure of the Hutchison device is unlike that the of present invention and relies on entirely different principles of operation and does not teach stock length adjustment.
U.S. Pat. No. 3,754,344 discloses a gun stock having a separate movable member which moves against the compression of a pair of helical springs enclosed within the main portion of the gun stock. The basic theory of this patent in providing a compressible gun stock is similar to that of the present invention, however the spring arrangements disclosed in the '344 patent are very limited in the amount of shock which can be absorbed and in the adjustments which can be made in the device, all of which disadvantages are overcome by the present invention.
A simple form of recoil pad for attachment to the butt end of a firearm's stock is shown in U.S. Pat. No. 4,922,641. This device utilizes a series of helical springs, a cushion of interior air and a compressible foam member to aid in overall compressibility. While the intent is the same as that of the present invention, the structure and operation of the device is entirely distinct from that of the present invention.
With the disadvantages and limitations of the prior art in mind, it is the primary object of the invention to provide a recoil absorbing stock for rifles, shotguns and automatic rifles which is adjustable and is more effective for its purpose than any of the devices of the prior art.
A second object of the invention is to provide an adjustable length firearm stock together with a complimentary recoil reduction mechanism.
Another objective of the invention is to provide a firearm stock having separate and independent adjustments for stock length and recoil absorption characteristics where one does not affect the other.
A still further object of the invention is to double the utility of a recoil reduction mechanism by having it also serve as the stock of the firearm, capable of conveniently mounting a shooter's cheek piece.
Yet another object of the invention is to provide a recoil absorbing device utilizing disc springs in a novel manner in order to achieve maximum energy absorption with minimum of weight and space considerations.